package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.RedisData;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.time.LocalDateTime;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Autowired
    private StringRedisTemplate stringRedisTemplate;
    @Override
    public Result queryById(Long id) {
        //缓存穿透解决
        //Shop shop = queryWithPassThrough(id);

        //互斥锁解决缓存击穿
        //Shop shop = queryWithMutex(id);

        //逻辑过期解决缓存击穿
        Shop shop = queryWithLogicalExpire(id);
        if (shop == null) {
            return Result.fail("店铺信息不存在");
        }
        return Result.ok(shop);
    }
    //获取锁
    private boolean tryLock(String key){
        Boolean b = stringRedisTemplate.opsForValue().setIfAbsent(key,"1",10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(b);
    }
    //释放锁
    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }

    //创建线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);


    //逻辑过期解决缓存穿透
    public Shop queryWithLogicalExpire(Long id){
        String key= CACHE_SHOP_KEY + id;
        //1.从Redis中查询
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            //未命中返回空值
            return null;
        }
        //命中，反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        JSONObject redisDataData = (JSONObject)redisData.getData();
        Shop shop = JSONUtil.toBean(redisDataData, Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            //未过期，直接返回商品信息
            return shop;
        }
        //已过期，需要缓存重建
        //获取互斥锁
        String lockKey = LOCK_SHOP_KEY+id;
        //判断是否获取成功
        if (tryLock(lockKey)) {
            //TODO 获取锁成功，开启独立线程
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    this.saveShop2Redis(id, 20L);
                }catch (Exception e){
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }
        //返回过期的商铺信息
        return shop;
    }

    //互斥锁解决缓存击穿
    public Shop queryWithPassThrough(Long id){
        String key= CACHE_SHOP_KEY + id;
        //1.从Redis中查询
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            //3.不存在，根据id查询数据库
            Shop shop = getById(id);
            //5.数据库不存在，返回错误
            if (shop == null) {
                //1.将空值写入Redis
                stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
                //2.返回错误信息
                return null;
            }
            //6.存在，写入Redis  添加过期时间
            stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
        }
        //命中但是为空值
        if(shopJson == ""){
            return null;
        }
        //4.存在，直接返回
        Shop shop = JSONUtil.toBean(shopJson, Shop.class);
        //7.返回
        return shop;
    }

    public Shop queryWithMutex(Long id){
        String key= CACHE_SHOP_KEY + id;
        //1.从Redis中查询
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            //3.1实现缓存重建
            //3.11获取互斥锁
            String lockKey = LOCK_SHOP_KEY+id;
            Shop shop= null;
            try {
                boolean isLock = tryLock(lockKey);
                //3.12判断是否获取成功
                if (!isLock) {
                    //3.13失败，休眠重试
                    Thread.sleep(50);
                    return queryWithMutex(id);//循环重试
                }

                //3.14成功，根据id查询数据库
                 Thread.sleep(200);//
                 shop = getById(id);
                //3.2数据库不存在，返回错误
                if (shop == null) {
                    //3.3将空值写入Redis
                    stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
                    //3.4返回错误信息
                    return null;
                }
                //3.5存在，写入Redis  添加过期时间
                stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
            }catch(InterruptedException e){
                throw new RuntimeException(e);
            }finally {
                //3.6释放锁
                unLock(lockKey);
            }
            //3.7返回
            return shop;
        }
        //命中但是为空值
        if(shopJson == ""){
            return null;
        }
        //4.存在，直接返回
        Shop shop = JSONUtil.toBean(shopJson, Shop.class);
        //5.返回
        return shop;
    }

    public void saveShop2Redis(Long id,Long expireSeconds) throws InterruptedException {
        //查询店铺信息
        Shop shop = getById(id);
        Thread.sleep(200);
        //封装逻辑过期
        RedisData redisData =new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        //写入Redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY+id,JSONUtil.toJsonStr(redisData));//永久有效，逻辑过期
    }
    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if (id == null) {
            return Result.fail("数据错误");
        }
        //1.写入数据库
        updateById(shop);
        //2.删除缓存
       stringRedisTemplate.delete(CACHE_SHOP_KEY+shop.getId());
       return Result.ok();
    }
}
